The correct answer is: A. Perfectly elastic.
A rectangular hyperbola is a type of demand curve where the quantity demanded is infinitely responsive to changes in price. This means that if the price of a good increases, consumers will demand zero units of the good, and if the price of a good decreases, consumers will demand an infinite number of units of the good.
Perfectly elastic demand is a special case of elastic demand, where the elasticity of demand is equal to infinity. This means that a small change in price will lead to a large change in quantity demanded.
Unit elastic demand is a special case of elastic demand, where the elasticity of demand is equal to one. This means that a change in price will lead to an equal change in quantity demanded.
Perfectly inelastic demand is a special case of inelastic demand, where the elasticity of demand is equal to zero. This means that a change in price will not lead to any change in quantity demanded.
Highly elastic demand is a type of demand where the elasticity of demand is greater than one. This means that a small change in price will lead to a large change in quantity demanded.
In conclusion, the elasticity of demand for a good with a rectangular hyperbola demand curve is perfectly elastic.